Continuous preparation of nitrosyl fluoride

ABSTRACT

A process and apparatus for the continuous production of nitrosyl fluoride from nitrite and hydrogen fluoride. Nitrite solids and hydrogen fluoride are separately introduced and blended into nitrosyl fluoride so as to form a reaction mixture within which the nitrite and the hydrogen fluoride react to produce additional nitrosyl fluoride. The hydrogen fluoride is introduced into the reaction mixture spaced away from where the nitrite is introduced into the reaction mixture so that the hydrogen fluoride and the nitrite separately mix into the nitrosyl fluoride and are diluted therein before mixing with each other, thereby avoiding a violent reaction between the hydrogen fluoride and the nitrite.

This invention relates to the preparation of nitrosyl fluoride, whichhas utility in diazotization reactions.

BACKGROUND OF THE INVENTION

Various methods have been used to form nitrosyl fluoride (NOF). Oneknown method is to add a nitrite directly to an amine solution inhydrogen fluoride (HF). The direct addition of the nitrite to the HFsolution of amine triggers a highly exothermic reaction which involvesthe formation of an unstable intermediate diazonium salt. Such salts areprone to decompose in a runaway reaction, producing safety hazards.

Attempts have also been made at producing NOF as a separate solution.The proposed processes have not proven satisfactory, as they generallyfail to implement specific design provisions to deal with yield andoperational problems, and typically, have been performed as a batchprocedure. The batch makeup of NOF in HF is very exothermic. Localhotspots often account for yield losses of 3% or more, and as thevolatile nitrite becomes a concentrated solution, the conversionby-products can contribute to high corrosion rates of the equipment usedin the reaction.

When NOF solution is produced by a batch method, the addition of nitritesolids to anhydrous HF can generate a substantial amount of HF vapor.This HF vapor alters the material balance of the components and makesfurther processing difficult. Thus, vapor loss control equipment isneeded under these circumstances to capture the HF released and preventalteration of the material balance.

Batch processes for the production of NOF proceed by the incrementaladdition of nitrite to HF. Thus, there is no steady-state reactionmixture with the result that the reaction environment is continuouslyvarying. In turn, this produces safety and containment engineeringproblems, the solutions of which have proven difficult and expensive.

Therefore a need exists for an alternative method of producing NOF whichis safer to use, permits higher yields, improves process control, andreduces by-product corrosivity problems.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic illustration of a single reactor embodiment forthe continuous production of nitrosyl fluoride.

FIG. 2 is a schematic illustration of a dual reactor embodiment for thecontinuous preparation of nitrosyl fluoride.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, a reactor 10 is provided, within which areaction mixture is formed for the production of nitrosyl fluoride. Inthe embodiment shown, reactor 10 is a continuous stirred tank reactorhaving a stirring means 12 operated by a motor 14.

According to this embodiment, nitrosyl fluoride (NOF) solution isintroduced into the bottom of reactor 10 through feed line 16. In orderto form additional nitrosyl fluoride, hydrogen fluoride (HF) and nitriteare separately introduced into reactor 10 and separately mixed into thenitrosyl fluoride present in reactor 10 to form reaction mixture 18.Thus, the hydrogen fluoride and nitrite are diluted in the reactionmixture before mixing with each other so as to avoid a violent reactionbetween the hydrogen fluoride and the nitrite.

In the embodiment shown in FIG. 1, nitrite, such as sodium nitrite orpotassium nitrite, in the form of pellets or granules, is fed into thetop of the reactor through inlet 20. In the illustrated embodiments, thesource of the nitrite is a solids feeding system 22 having a dual-valvefeeder 24, including valves 26 and 28, and a source of nitrogen gas 30for nitrogen-purging of the nitrite.

Hydrogen fluoride (preferably anhydrous HF) is introduced into reactionmixture 18 via a dip-pipe sub-surface feed input 32 from an HF source34. The area designated 36 in FIG. 1 is a local HF mixing zone wherein,for example, a radial turbine is utilized to mix HF into the solution.By spacing the sources of nitrite and hydrogen fluoride apart, thereactants are allowed to mix into the bulk phase before they encountereach other, so that the hydrogen fluoride and nitrite do not reactviolently during the formation of nitrosyl fluoride.

Nitrite and hydrogen fluoride can be continuously added to the reactionmixture 18 in reactor 10, or cyclically added over a cycle timesufficiently short so as not to vary substantially the bulk composition.

Nitrosyl fluoride exits the reactor through outlet 38. Outlet 38 of tank10 is an overflow-type outlet, whereby solution flows out of tank 10 atthe same rate that material is introduced therein, so that the reactionmixture 18 is maintained at a constant volume. Advantageously, a baffle40 is provided over outlet 38 to force the upflow of solution as itexits the reactor, thereby allowing coarse solids to settle out andremain in the reactor. A pump 42 is provided along line 44 to pump thesolution through a cooler 46. Cooler 46 can use any suitable coolingmeans, such as a shell and tube system with a refrigerated water supplyand return. The cooled solution of nitrosyl fluoride is split at 48,with a small portion thereof going to diazotization, and the bulk of thenitrosyl fluoride being returned to reactor 10 via line 16. Escapinghydrogen fluoride vapor is removed from the top of reactor 10 throughvent 50, and passed through line 52 to a hydrogen fluoride scrub system54.

FIG. 2 illustrates a preferred dual reactor system for the continuousproduction of nitrosyl fluoride, wherein features having the samefunction as those shown in FIG. 1 are given the same reference numeralin FIG. 2. In the embodiment shown in FIG. 2, a second reactor 10a isprovided which also advantageously is a continuous stirred tank reactorhaving a stirring means 12a operated by a motor 14a associatedtherewith. According to this embodiment, a line 56 connects the outletof reactor 10 with an inlet 58 of reactor 10a into which the reactionmixture 18a passes. The nitrosyl fluoride exits reactor 10a through anoutlet 60 in the bottom of reactor 10a and is pumped through line 44a bypump 42a into cooler 46. The nitrosyl fluoride then is split at 48, withthe bulk of it being returned to reactor tank 10 to be mixed withadditional nitrite and hydrogen fluoride.

In both the illustrated embodiments, a constant volume reservoir ofreaction mixture is provided in a first reactor, which reservoir is of asufficient volume to dampen out flow effects from an external coolingloop. Additionally, the reservoir volume is sufficient to keep the tworeactant input streams separated from each other, such that eachreactant is mixed into the bulk phase prior to encountering the otherreactant. Simultaneously with the introduction of nitrite into thereservoir, a second input reactant stream of hydrogen fluoride also isintroduced. This input stream is physically separated from the nitritestream, thereby allowing both reactants to be mixed into the bulk phaseNOF prior to encountering each other.

As the reactants are introduced into the first reactor, a reactionmixture is formed and nitrosyl fluoride solution begins to be produced.This nitrosyl fluoride solution can be recovered from the first reactorwithout further processing. If that is to occur, the solution isremoved, preferably by an overflow means, cooled, and passed todiazotization reaction vessels. In preferred embodiments, only a portionof the NOF solution will be passed through to diazotization, with theremainder being fed back into the constant volume reservoir of reactor10. This has the effect of maintaining the reservoir volume constant aswell as controlling the temperature within the reactor, and additionallycontrolling the NOF concentration at a substantially constant value.

In the two reaction vessel system, the NOF produced in the first reactoris transferred to a second reactor which is similar to the firstreactor. For this system, the second reactor only needs a single feedintroduction point for receiving the reaction mixture from the firstreactor. Generally, overflow means connecting the two reactors is asufficient method of transfer. However, other transfer means includingactive means, can be used.

The second reactor will have at least one discharge means for removingNOF solution after a further dissolution reaction has occurred. Thesecond reactor functions as a pass-through vessel for facilitatingfurther reaction. Performance of the system is enhanced over a singlestage reactor with respect to solids retention and dissolution. As notedabove, the discharge means in the second reactor is advantageouslylocated at the bottom thereof. NOF solution is withdrawn and pumpedthrough a cooler back into the first reactor. External cooling allowsthe heat of reaction to be removed from the reactor vessels, therebyreducing local hot spots. Most desirably, the returning NOF is fed intoa feed introduction point located at the bottom of the first reactor.This enhances mixing and sweeps undissolved solids off the reactorbottom, thereby avoiding risks of hazardous accumulations.

Subsequently to cooling, but prior to being returned to the firstreactor, the NOF solution can be split into separate streams with aportion being recovered. This recovered portion can be passed through afilter, which traps any residual solid nitrite particles and allows themto dissolve. Such filtering protects the flow control valves used in thedownstream diazotization. If desired, more than two reactors can be usedin the process, and such a configuration is encompassed within the scopeof the present invention.

Utilizing the described process results in a much slower energy releaseduring the desired reaction and greatly reduces both vapor flash andlocal heat-up. The dissolution rate of the added nitrite is sufficientlyslowed by the present method to allow the heat of reaction to be gentlydissipated into the solution with minimal local effects. Thus, improvedyields over prior art processes can be expected.

The present process improves material balance, by the suppression of NOFdecomposition and HF flashing from local overheating, allowing improvedcontrol of the composition of the NOF solution. The need for repeatedassessment of the composition of NOF from each batch, which is requiredby the prior art, is reduced if not eliminated. Overcharges of NOF intothe diazotization process are effectively eliminated, thus assuring highNOF conversion during diazotization. Undesirable tarlike by-productsfound in subsequent reaction steps when excess NOF in diazonium is usedare substantially reduced over known processes.

The enhanced compositional control of the present process alsosubstantially eliminates the formation of corrosive by-products producedby prior art processes. In turn, this allows the identification and useof a particularly desirable construction material for a given narrowoperating environment. Of course, this construction material will varydepending upon the operating environment selected, but the compositionof choice easily can be determined by those of ordinary skill in the artof chemical engineering.

The continuous NOF make-up process is much safer than the prior artprocesses. Nitrite is added to a full or a nearly full strength NOFsolution. This greatly reduces the energy release rate upon reaction.The reaction is spread throughout the reaction volume, thereby avoidingsevere local hotspots and flashing. When simultaneous addition ofanhydrous HF is performed using a dip-pipe sub-surface inlet, thesimultaneous sub-surface addition thereof helps the two feeds toindependently mix with the NOF prior to contacting each other. It alsoencourages cross-flow of the lighter HF and the heavier nitrite feeds inthe constant volume. Therefore, there is little or no risk of theviolent reaction which is seen with the addition of nitrite solids toanhydrous HF in the prior art.

The invention will be further described in reference to the followingexample, which is not intended to be limiting.

EXAMPLE I

This example utilizes a dual reactor system as schematically shown inFIG. 2. The primary dissolver reactor 10 has a working volume ofapproximately 50 gallons. Nitrosyl fluoride solution is fed into primaryreactor 10 via line 16 at a temperature of approximately 0° C. and at arate of about 8.5 gallons per minute (gpm). Reactants sodium nitrite(NaNO₂) and hydrogen fluoride are fed into the reaction mixture at amole ratio of approximately 12 moles HF/1 mole NaNO₂ . Although pelletsof NaNO₂ can be used (with a minimum residence time within reactor 10 ofabout 3 minutes), sodium nitrite granules are preferred. The minimumresidence time when using sodium nitrite granules is about 1 minute,with preferred residence times of about 6-10 minutes. Hydrogen fluorideis fed into reactor 10 at a rate of about 155 lb/hr (7.8 lb mol/hr), andsodium nitrite is fed into the reaction mixture at a rate of about 44lb/hr (0.65 lb mol/hr). At an NOF feed rate into reactor 10 of 8.5 gpm,the above-described reaction mixture has a residence time within reactor10 of about 6 minutes.

The reaction mixture exits outlet 38 of tank 10 at a rate of about 8.7gpm and flows into the fines dissolver reactor 10a which has a workingvolume of about 50 gallons. The materials continued to react withinreactor 10a to form nitrosyl fluoride, which is withdrawn from reactor10a at outlet 60 at the bottom thereof. Nitrosyl fluoride solutionexiting tank 10a is at a temperature of about 10° C., and is drawnthrough line 44a by pump 42a through a shell and tube-type cooler 46having a refrigerated water supply and return. Cooler 46 cools thenitrosyl fluoride solution to about 0° C. before the solution is passedby a flow-splitter 48. A flow-control valve 62 allows about 16.8 gph ofthe nitrosyl fluoride solution to pass to diazotization, while recyclingabout 97% of the solution to the reaction mixture 18 in reactor tank 10.In reactor 10, the temperature of the reaction mixture increases toabout 10° C. due to heat produced by the reaction of hydrogen fluorideand nitrite in the production of nitrosyl fluoride.

EXAMPLE II

This example utilizes a dual reactor system as schematically shown inFIG. 2. The primary dissolver reactor 10 has a working volume ofapproximately 195 gallons. Nitrosyl fluoride solution is fed intoprimary reactor 10 via line 16 at a temperature of approximately 0° C.and at a rate of about 33 gallons per minute (gpm). Reactants sodiumnitrite (NaNO₂) and hydrogen fluoride are fed into the reaction mixtureat a mole ratio of approximately 12 moles HF/1 mole NaNO₂. Althoughpellets of NaNO₂ can be used (with a minimum residence time withinreactor 10 of about 3 minutes), sodium nitrite granules are preferred.The minimum residence time when using sodium nitrite granules is about 1minute, with preferred residence times of about 6-10 minutes. Hydrogenfluoride is fed into reactor 10 at a rate of about 605.5 lb/hr (30.25 lbmol/hr), and sodium nitrite is fed into the reaction mixture at a rateof about 174 lb/hr (2.52 lb mol/hr). At an NOF feed rate into reactor 10of 33 gpm, the above-described reaction mixture has a residence timewithin reactor 10 of about 6 minutes.

The reaction mixture exits outlet 38 of tank 10 at a rate of about 34gpm and flows into the fines dissolver reactor 10a which has a workingvolume of about 195 gallons. The materials continued to react withinreactor 10a to form nitrosyl fluoride, which is withdrawn from reactor10a at outlet 60 at the bottom thereof. Nitrosyl fluoride solutionexiting tank 10a is at a temperature of about 10° C., and is drawnthrough line 44a by pump 42a through a shell and tube-type cooler 46having a refrigerated water supply and return. Cooler 46 cools thenitrosyl fluoride solution to about 0° C. before the solution is passedby a flow-splitter 48. A flow-control valve 62 allows about 1.1 gpm ofthe nitrosyl fluoride solution to pass to diazotization, while recyclingabout 97% of the solution to the reaction mixture 18 in reactor tank 10.In reactor 10, the temperature of the reaction mixture increases toabout 10° C. due to heat produced by the reaction of hydrogen fluorideand nitrite in the production of nitrosyl fluoride.

EXAMPLE III

This example utilizes a dual reactor system as schematically shown inFIG. 2. The primary dissolver reactor 10 has a working volume ofapproximately 390 gallons. Nitrosyl fluoride solution is fed intoprimary reactor 10 via line 16 at a temperature of approximately 0° C.and at a rate of about 66 gallons per minute (gpm). Reactants sodiumnitrite (NaNO₂) and hydrogen fluoride are fed into the reaction mixtureat a mole ratio of approximately 12 moles HF/1 mole NaNO₂. Althoughpellets of NaNO₂ can be used (with a minimum residence time withinreactor 10 of about 3 minutes), sodium nitrite granules are preferred.The minimum residence time when using sodium nitrite granules is about 1minute, with preferred residence times of about 6-10 minutes. Hydrogenfluoride is fed into reactor 10 at a rate of about 1211 lb/hr (60.5 lbmol/hr), and sodium nitrite is fed into the reaction mixture at a rateof about 348 lb/hr (5.04 lb mol/hr). At an NOF feed rate into reactor 10of 66 gpm, the above-described reaction mixture has a residence timewithin reactor 10 of about 6 minutes.

The reaction mixture exits outlet 38 of tank 10 at a rate of about 68gpm and flows into the fines dissolver reactor 10a, which has a workingvolume of about 390 gallons. The materials continued to react withinreactor 10a to form nitrosyl fluoride, which is withdrawn from reactor10a at outlet 60 at the bottom thereof. Nitrosyl fluoride solutionexiting tank 10a is at a temperature of about 10° C., and is drawnthrough line 44a by pump 42a through a shell and tube-type cooler 46having a refrigerated water supply and return. Cooler 46 cools thenitrosyl fluoride solution to about 0° C. before the solution is passedby a flow-splitter 48. A flow-control valve 62 allows about 2.2 gpm ofthe nitrosyl fluoride solution to pass to diazotization, while recyclingabout 97% of the solution to the reaction mixture 18 in reactor tank 10.In reactor 10, the temperature of the reaction mixture increases toabout 10° C. due to heat produced by the reaction of hydrogen fluorideand nitrite in the production of nitrosyl fluoride.

EXAMPLE IV

This example utilizes a dual reactor system as schematically shown inFIG. 2. The primary dissolver reactor 10 has a working volume ofapproximately 780 gallons. Nitrosyl fluoride solution is fed intoprimary reactor 10 via line 16 at a temperature of approximately 0° C.and at a rate of about 132 gallons per minute (gpm). Reactants sodiumnitrite (NaNO₂) and hydrogen fluoride are fed into the reaction mixtureat a mole ratio of approximately 12 moles HF/1 mole NaNO₂. Althoughpellets of NaNO₂ can be used (with a minimum residence time withinreactor 10 of about 3 minutes), sodium nitrite granules are preferred.The minimum residence time when using sodium nitrite granules is about 1minute, with preferred residence times of about 6-10 minutes. Hydrogenfluoride is fed into reactor 10 at a rate of about 2422 lb/hr (121 lbmol/hr), and sodium nitrite is fed into the reaction mixture at a rateof about 696 lb/hr (10.08 lb mol/hr). At an NOF feed rate into reactor10 of 132 gpm, the above-described reaction mixture has a residence timewithin reactor 10 of about 6 minutes.

The reaction mixture exits outlet 38 of tank 10 at a rate of about 136gpm and flows into the fines dissolver reactor 10a which has a workingvolume of about 780 gallons. The materials continued to react withinreactor 10a to form nitrosyl fluoride, which is withdrawn from reactor10a at outlet 60 at the bottom thereof. Nitrosyl fluoride solutionexiting tank 10a is at a temperature of about 10° C., and is drawnthrough line 44a by pump 42a through a shell and tube-type cooler 46having a refrigerated water supply and return. Cooler 46 cools thenitrosyl fluoride solution to about 0° C. before the solution is passedby a flow-splitter 48. A flow-control valve 62 allows about 4.4 gpm ofthe nitrosyl fluoride solution to pass to diazotization, while recyclingabout 97% of the solution to the reaction mixture 18 in reactor tank 10.In reactor 10, the temperature of the reaction mixture increases toabout 10° C. due to heat produced by the reaction of hydrogen fluorideand nitrite in the production of nitrosyl fluoride.

EXAMPLE V

This example utilizes a dual reactor system as schematically shown inFIG. 2. The primary dissolver reactor 10 has a working volume ofapproximately 1,560 gallons. Nitrosyl fluoride solution is fed intoprimary reactor 10 via line 16 at a temperature of approximately 0° C.and at a rate of about 264 gallons per minute (gpm). Reactants sodiumnitrite (NaNO₂) and hydrogen fluoride are fed into the reaction mixtureat a mole ratio of approximately 12 moles HF/1 mole NaNO₂. Althoughpellets of NaNO₂ can be used (with a minimum residence time withinreactor 10 of about 3 minutes), sodium nitrite granules are preferred.The minimum residence time when using sodium nitrite granules is about 1minute, with preferred residence times of about 6-10 minutes. Hydrogenfluoride is fed into reactor 10 at a rate of about 4844 lb/hr (242 lbmol/hr), and sodium nitrite is fed into the reaction mixture at a rateof about 1,392 lb/hr (20.16 lb mol/hr). At an NOF feed rate into reactor10 of 264 gpm, the above-described reaction mixture has a residence timewithin reactor 10 of about 6 minutes.

The reaction mixture exits outlet 38 of tank 10 at a rate of about 272gpm and flows into the fines dissolver reactor 10a which has a workingvolume of about 1824 gallons. The materials continued to react withinreactor 10a to form nitrosyl fluoride, which is withdrawn from reactor10a at outlet 60 at the bottom thereof. Nitrosyl fluoride solutionexiting tank 10a is at a temperature of about 10° C., and is drawnthrough line 44a by pump 42a through a shell and tube-type cooler 46having a refrigerated water supply and return. Cooler 46 cools thenitrosyl fluoride solution to about 0° C. before the solution is passedby a flow-splitter 48. A flow-control valve 62 allows about 8.8 gpm ofthe nitrosyl fluoride solution to pass to diazotization, while recyclingabout 97% of the solution to the reaction mixture 18 in reactor tank 10.In reactor 10, the temperature of the reaction mixture increases toabout 10° C. due to heat produced by the reaction of hydrogen fluorideand nitrite in the production of nitrosyl fluoride.

Since many modifications, variations, and changes in detail may be madeto the described embodiments, it is intended that all matter in theaforegoing description and shown in the accompanying drawings beinterpreted as illustrative and not in a limiting sense.

Since many modifications, variations, and changes in detail may be madeto the described embodiments, it is intended that all matter in theaforegoing description and shown in the accompanying drawings beinterpreted as illustrative and not in a limiting sense.

What is claimed is:
 1. A process for the preparation of nitrosylfluoride, comprising separately introducing and blending nitrite andhydrogen fluoride into nitrosyl fluoride solution so as to form areaction mixture within which the nitrite and the hydrogen fluoridereact so as to produce additional nitrosyl fluoride, and removingnitrosyl fluoride produced in the reaction mixture, wherein the reactionmixture is maintained at a substantially constant volume during theintroducing and removing steps, and wherein said hydrogen fluoride isintroduced into said reaction mixture spaced away from where saidnitrite is introduced into said reaction mixture so that the hydrogenfluoride and the nitrite independently mix into said nitrosyl fluoridesolution and are diluted therein before mixing with each other, therebyavoiding a violent reaction between the hydrogen fluoride and thenitrite.
 2. The process of claim 1 wherein said nitrite is continuouslyintroduced into said reaction mixture.
 3. The process of claim 1 whereinsaid hydrogen fluoride is continuously introduced into said reactionmixture.
 4. The process of claim 1 wherein nitrite and hydrogen fluorideare continuously introduced into said reaction mixture spaced apart, andwherein nitrosyl fluoride is continuously introduced into one portion ofthe reaction mixture while nitrosyl fluoride formed in the reactionmixture is continuously removed from another portion of the reactionmixture.
 5. The process of claim 1 wherein the hydrogen fluoride iscyclically introduced into said reaction mixture.
 6. The process ofclaim 1 wherein said nitrite is cyclically introduced into said reactionmixture.
 7. The process of claim wherein the nitrite and hydrogenfluoride are cyclically and simultaneously introduced into said reactionmixture spaced apart.
 8. The process of claim 7 wherein nitrosylfluoride is continuously introduced into one portion of the reactionmixture while nitrosyl fluoride formed in the reaction mixture iscontinuously removed from another portion of said reaction mixture.
 9. Aprocess for the continuous preparation of nitrosyl fluoride, comprisingcontinuously and separately introducing and blending nitrite andhydrogen fluoride into nitrosyl fluoride solution so as to form areaction mixture within which the nitrite and the hydrogen fluoridereact to produce additional nitrosyl fluoride, and removing nitrosylfluoride produced in the reaction mixture, wherein said hydrogenfluoride is introduced into said reaction mixture spaced away from wheresaid nitrite is introduced into said reaction mixture so that thehydrogen fluoride and the nitrite independently mix into said nitrosylfluoride and are diluted therein before mixing with each other, therebyavoiding a violent reaction between the hydrogen fluoride and thenitrite.
 10. The process of claim 9 wherein nitrosyl fluoride iscontinuously introduced into one portion of the reaction mixture andnitrosyl fluoride is continuously removed from another portion of thereaction mixture.
 11. The process of claim 9 wherein said reactionmixture is initially formed in a first reactor, further comprisingtransferring said reaction mixture to a second reactor to permit furtherreaction of said reaction mixture to occur in the second reactor. 12.The process of claim 9 further comprising
 13. The process of claim 12wherein said cooling is external to said reactor.
 14. The process ofclaim 13, further comprising recycling at least a portion of said cooledsolution back into said reactor.
 15. The process of claim 11, furthercomprising returning at least a portion of said reaction mixture fromsaid second reactor to said first rector to maintain a constant volumereservoir of reaction mixture in the first reactor.
 16. The process ofclaim 15, further comprising cooling said returning portion of reactionmixture.
 17. The process of claim 9, wherein said hydrogen fluoride isintroduced by a dip-pipe sub-surface feed input.
 18. The process ofclaim 16, wherein said returned portion is fed into said first reactorat the bottom of said reactor.